1. Field of the Invention
The present invention relates to an optical apparatus for emitting light such as a laser beam collimator unit used in an image recording apparatus for recording an image by scanning a laser beam modulated according to an image signal on a recording medium, or a pickup unit of an optical disk using a semi-conductor laser light source, and to an automatic adjustment apparatus therefor.
2. Related Background Art
In recent years, image recording apparatuses such as laser beam printers (LBPs) for recording an image by scanning a laser beam have been widely used. A laser scanning apparatus used in the image recording apparatus will be described below with reference to FIG. 15.
A semi-conductor laser light source 1X, a collimator lens 2X, an imaging optical system 3X, a polygonal mirror 4X as a deflector, an f.theta. lens 5X comprising a spherical lens, a toric lens and the like, and a photosensitive drum 6X as a recording medium are arranged in the order named along an optical path. A laser beam modulated according to an image signal and emitted from the semi-conductor laser light source 1X is collimated by the collimator lens 2X, and the collimated beam is transmitted through the imaging optical system 3X. The beam is then deflected and scanned by the polygonal mirror 4X, and forms an image on the photosensitive drum 6X by the f.theta. lens 5X. In this manner, in general, light output from the semi-conductor laser light source 1X radially diverges from the light emitting point. For this reason, when the laser light source is used in, e.g., an LBP, an optical apparatus for emitting light (a laser unit) for collimating output light using the collimator lens 2X is used.
FIG. 16 is a longitudinal sectional view of a conventional optical apparatus for emitting light (laser unit) of this type. The semi-conductor laser light source 1X is urged against a base 7X by an electrical circuit board 9X and a spring 11X. The electrical circuit board 9X is fixed to the base 7X by a screw 13X. A hollow holder 8X formed in a substantially convex shape mounts therein a lens-barrel 10X which incorporates a collimator lens 2X.
Upon adjustment of the focusing position and the irradiating position, the lens-barrel 10X is moved in an optical axis direction (a direction of an arrow A in FIG. 16), and is then held at a position where the diameter of a laser beam transmitted through the collimator lens 2X has a minimum value. Thereafter, an adhesive (not shown) is filled from a hole 14X into the holder 8X to fix the lens-barrel 10X to the holder 8X, thus adjusting the focusing position. Then, the base 7X of the semi-conductor laser light source 1X is two-dimensionally moved on a plane perpendicular to the optical axis of the light source 1X, so that the central axis of the lens-barrel 10X coincides with the optical axis of the light source 1X. After the position adjustment, the base 7X is fixed to the holder 8X by a screw 12X, thus adjusting the irradiating position.
Upon adjustment of the irradiating position, when the focusing position in the optical axis direction is shifted due to, e.g., deformation of the holder 8X, the optical apparatus for emitting light is discarded as a defective product. Alternatively, the adhesive is removed, and the lens-barrel 10X is moved in the optical axis direction again to correct the shift of the focusing position. Thereafter, an adhesive (not shown) is filled from the hole 14X into the holder 8X to fix the lens-barrel 10X to the holder 8X.
However, in the conventional optical apparatus for emitting light described above, there arise the following problems (1), (2), and (3):
(1) Since the focusing position and the irradiating position are adjusted by moving different members, the focusing position in a focusing direction is easily shifted upon adjustment of the irradiating position after the adjustment of the focusing position. Therefore, the focusing position must be adjusted again.
(2) Upon adjustment of the irradiating position, since the base for supporting the semi-conductor laser light source is fixed to the holder using a screw, a positional shift easily occurs, and this adjustment requires much time and skill.
(3) Since the holder as a member for adjusting the focusing position in the optical axis direction, and the base as a member for adjusting the irradiating position in a direction perpendicular to the optical axis are required, the number of components is increased, resulting in an increase in cost.